System and method for testing fuel tank integrity

ABSTRACT

The invention relates generally to a system and method for testing fuel evaporative systems, and more particularly to a stand-alone tank tester system (and method) for testing vehicle fuel tank integrity. Furthermore, a self-contained calibration tank with switchable leak sizes for calibrating the tank tester to multiple leak sizes is provided. Constant flow and vacuum methods for testing fuel tank integrity are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a divisional of U.S. patent application Ser. No.10/974,677, filed Oct. 28, 2004, now U.S. Pat. No. 7,168,297 whichclaims priority to U.S. Provisional Patent Application Ser. No.60/514,745 filed Oct. 28, 2003, which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The invention relates generally to a system and method for testing fuelevaporative systems, and more particularly to a stand-alone tank testersystem (and method) for testing vehicle fuel tank integrity.

BACKGROUND OF THE INVENTION

The loss of fuel from a vehicle fuel tank (and associated piping)through evaporation to the atmosphere may result in, among other things,undesirable hydrocarbon pollution.

Accordingly, many systems and methods have been developed to test thetank integrity of vehicle fuel systems, and to identify vehicles thatfail to comply with promulgated regulations and mandated guidelines(regardless of whether they are on the federal, state, or local level).

Unfortunately, many existing fuel tank integrity testing systems can beexpensive, cumbersome, and inconsistent. These and other drawbacksexist.

SUMMARY OF THE INVENTION

The invention solving these and other problems relates to a stand-alonetank tester system (and method) for testing vehicle fuel tank (or fuelsystem) integrity.

According to an embodiment of the invention, a system is provided for atank tester. The tank tester may perform various processes for testingfuel tank integrity, measurement of fuel tank volume, measurement offuel volume, measurement of vapor space, measurement of fueltemperature, or other tests. The tank tester may include acomputer-implemented component (“computer component”), a testingcomponent, a housing, a calibration tank, and/or other elements. In someembodiments, the tank tester may perform various calibration andself-test procedures which may be necessary for efficient and accurateexecution of fuel tank tests.

Computer Component

In one embodiment of the invention, the tank tester may include acomputer component. The computer component may include various softwareelements and computer hardware such as, for example, a processor board.The processor board may include a processor which may be or include, forinstance, any of the Intel ×86 PC/AT microprocessors or compatibleprocessors such as those available from Cyrix or AMD. The processorboard may also include one or more analog inputs with A/D convertersthat interface with various sensors, one or more digital outputs tointerface with one or more solenoids, and other elements. The processorboard may also include one or more serial ports that may interface withadditional equipment such as, for example, Emissions Inspection Systems(EIS) equipment, a modem, a real time clock, or other devices orelements. The processor board may also include one or more memorydevices. The one or more memory devices may include flash erasableprogrammable read-only-memory (FEPROM), a hard disk, or other datasuitable memory for data storage.

The computer component may also include a signal conditioning boardoperatively connected to the processor board. The signal conditioningboard may, among other things, condition electrical signals into and outfrom any sensors. The signal conditioning board may include a DC/DCpower supply. The signal conditioning board may also include a pressureswitch control for releasing pressure from the testing component(described in detail below) upon the existence of a predeterminedpressure within the testing component. The signal conditioning board mayfurther include one or more solenoid drivers for operating one or moresolenoids throughout the tank tester. One or more solenoids may beutilized to operate various elements of the testing component includingswitches, valves, or other elements.

The computer component may also include one or more sensors operativelyconnected to the processor board and/or the signal conditioning board.The one or more sensors may include pressure transducers, temperaturesensors, or other sensors for operation of the tank tester.

The computer component may also include external memory operativelyconnected to the processor board. The external memory may include flashmemory, a hard disk, or other suitable memory for storing run-timeprograms, vehicle databases, testing lookup tables, recent test results,or other data.

In one embodiment, the computer component may include or host anoperating application. The operating application may include one or moresoftware modules enabling the operation of, and user interaction with,the tank tester. The operating application may be based on any one ofmany computer programming languages such as, for example, C, C++, orother programming language.

The operating application may include software for fuel tank testing,inspection test procedures and criteria, security measures, utilities,ancillary modules, or other software. The features enabled may include,among other things, integrated calibration and self test procedures,outside ambient temperature measurement, internal tank tester pressuremeasurements, fuel tank pressure measurements, evaporative tests,constant flow determination of a tank leak, vapor space compensation,temperature compensation, Reid Vapor Pressure (RVP) compensation, vacuumtank integrity testing, hydrocarbon detection, constant pressure tankintegrity testing, use of vapor temperature for determination of liquidfuel temperature, interface with an Emissions Inspections System (EIS),or other features. One or more of the modules comprising the operatingapplication may be combined. For some purposes, not all modules may benecessary.

In one embodiment, the operating application may also include, or haveaccess to, data look-up tables, and may use table calls for fuel tankvapor space calculations, pass/fail decisions, and/or other calculationsand decisions. These tables may compensate for temperature and RVP whenmaking the vapor space calculations, pass/fail determinations, or othercalculations or decisions. In addition, the operating application maywrite test results and calibration test results to a record (“testrecord”).

In one embodiment, the computer component may include an interface thatenables one or more users to interact with the operating application.The interface may comprise a graphical user interface (GUI) presented toa user on a display device. A user may interact with the operatingapplication and the GUI via a user input device.

The computer component may also include other elements for the operationof the tank tester. As would be apparent to one skilled in the art,other configurations for the computer component may exist.

Testing Component

In one embodiment of the invention, the tank tester may include atesting component. The testing component may include a pressurized gassource, various pressure transducers, pressure regulators, valves,orifices, pneumatic pluming elements, or other elements for performingthe operations of the tank tester described herein.

In one embodiment, the pressurized gas source may contain or producepressurized gas for use in the tank tester. The pressurized gas maycomprise nitrogen, compressed air, or another gas. If the tank testeruses nitrogen as a pressurizing gas, then the nitrogen may be 98% pure.Other concentrations may be used. If the tank tester uses compressed airas a pressurizing gas, an air filter capable of removing harmfulcontaminants and moisture from the compressed air may be included. Thisfilter may ensure that no contaminants enter the tank tester that couldphysically block any orifice, or chemically contaminate the internalcomponents of the tester. The filter may be configured to filter down to5-micron size particles.

The pressurized gas source may be pneumatically connected to the variouspressure transducers, pressure regulators, valves, orifices, or otherelements included in the testing component of the tank tester.

The testing element may also include an outlet hose. The outlet hose mayinterface with a tank adaptor at one of its ends. The tank adaptor mayinclude any of a set of fuel filler neck adaptors (“tank adaptors”) thatprovide connectivity to various vehicles.

According to an embodiment of the invention, the tank adaptor, outlethose, and any pneumatic conduit or gasket materials may be comprised ofmaterial which may be pliable and impermeable to some or all gasolineconstituents including, for instance, Methyl Tertiary Butyl Ether(MTBE), ethanol, and methanol. Material exhibiting these properties isknown in the art. Furthermore, the tank adaptor, the outlet hose, andother elements within testing component may be fitted with quickdisconnect couplers that facilitate easy and rapid connection anddisconnection from the vehicle.

Housing and Calibration Tank

In some embodiments of the invention, the tank tester may include ahousing that may enclose one or more components of the tank tester. Inother embodiments of the invention, the housing may support one or morecomponents of the tank tester. These components may be supported eitherinternally within the housing, externally to the housing, or partiallyinternal and partially external to the housing. In another embodiment,the housing may comprise a custom impact-resistant plastic enclosurewith a carrying strap and/or handle.

In one embodiment of the invention, a calibration tank may be includedwith the tank tester. The calibration tank may form a predeterminedvolume that may be pressurized. In some embodiments, the calibrationtank may be supported internally within the housing. In someembodiments, the housing itself (or part of the housing) may form thecalibration tank. In one embodiment, the calibration tank may include abladder (not otherwise illustrated). In some embodiments, the bladdermay conform itself within the housing. In another embodiment, thehousing and/or the calibration tank may include a blow-molded case (nototherwise illustrated) with a volume that may be pressurized. Asdiscussed above, the case may be formed, machined, or molded to have anypredetermined volume.

The volume of the calibration tank may comprise one gallon, two gallons,five gallons, ten gallons, or any other predetermined volume. In someembodiments, this volume may be adjustable. The calibration tank mayserve as a component for performing various calibration procedures(described in detail below) enabling efficient and accurate operation ofthe tank tester.

Calibration

According to an embodiment of the invention, the tank tester may includea calibration module. The calibration module may enable calibration ofthe various elements of the tank tester. Calibration may include one ormore of the following processes: self-test of inlet pressure, self-testof transducers, self-test of temperature sensors, sensor check/zero withpressure disconnected, sensor check/zero with pressure connected, systemleak/decay check with no tank, tank volume check with no leak, passingtank calibration, failing tank calibration, or other process.

As mentioned above, the calibration module may utilize a calibrationtank that contains a known, predetermined volume (or vapor space). Inone embodiment, the calibration tank may include switchable calibratedleak standards. For example, the calibration tank may containpurposefully designed leaks of varying sizes, one or more of which maybe used to simulate fuel tank leaks of differing degrees.

According to one embodiment, the calibration module may utilize aninternal clock to determine when calibration is due. As an example, thecalibration module may automatically lock out test procedures on thetank tester every 72 hours pending a successful completion of one ormore calibration procedures. Other time intervals may be used.

According to an embodiment, the calibration module may perform a systemtest for the tank tester's overpressure function. This system testmonitors the tank tester's ability to disable the tank tester in theevent that over pressurization of a calibration tank or fuel tankoccurs. The tank tester may be capable of resuming normal operationafter the overpressure condition has been eliminated and the tank testersuccessfully completes the calibration procedure. For a failedoverpressure test, the tank tester may prevent further testing for apredetermined period of time, but may allow subsequent attempts tosuccessfully complete calibration procedures, self-tests, or systemtests.

Upon successful completion of a calibration procedure, the calibrationmodule may write the results to a calibration record with the date andtime. The calibration module may then start a clock to time-out the nextcalibration due date and time according to a predetermined time period.The new record may be recorded to the calibration record. The datarecorded in the calibration record (regardless of failure or passage)may include Station ID (facility conducting test), Tester ID (personconducting test), Calibration ID (the specific calibration iteration),Date/Time of Calibration, Software Version, Pressure Decay Results,Vapor Space Results, Simulated Test Results, Overall Calibration Result,Calibration Error, Date/Time of Next Calibration Due, or other data. Tocalculate the next time due, the software may add the predetermined timeperiod to the current calibration date and time. Once calibration hasbeen successfully completed, the calibration module may allow testing tooccur.

If the tank tester fails any portion of a calibration test, a user maybe prompted to perform subsequent calibration procedures or contact adesignated service provider for repairs. According to one embodiment,when service of the tank tester is required, the tank tester may notallow further tank testing or manual mode pressurization to be performeduntil full function has been restored by an authorized or designatedservice representative.

Testing

Fuel Evaporative Test

According to an embodiment of the invention, the tank tester may includea test module. The test module may be utilized to conduct various fueltank tests such as, for example, a fuel evaporative test. A fuelevaporative test may be performed to determine or calculate of the sizeof a hole in a fuel tank of unknown volume.

During a fuel evaporative test, the tank tester may pressurize a fueltank. During pressurization, the tank tester may determine if themaximum allowable fill time has been exceeded. If the fuel tank cannotbe pressurized to a predetermined pressure in a predetermined amount oftime, a gross leak may be present. If the fuel tank passes the fill-timeportion of the test (indicating no gross leak), the test module maydetermine whether an otherwise unacceptable leak exists in the fuel tank(i.e., pass or fail). In accordance with this test, the tank tester maycalculate the vapor space within the fuel tank being tested.

Flow Method

In another embodiment of the invention, the test module of the tanktester may perform a fuel evaporative test using a “flow method.” Inthis embodiment, the testing component of the tank tester may have twofilling paths: Fast Fill Flow and Slow Fill Flow.

Using the Fast Fill Flow path, a fuel tank may be pressurized to apredetermined pressure level such as, for example, 14″ H₂O at a rate ofapproximately 8.5 standard liters per minute (SLPM). Once the desiredpressure is achieved, the tank tester may switch to the Slow Fill Flowpath. The Slow Fill Flow path may have an orifice and a precisionpressure regulator set to a predetermined pressure level such as, forexample, 14″ H₂O. The precision pressure regulator attempts to maintaina constant pressure in the tank. If the tank has no leak, there will beno flow. If the tank has a leak, the flow rate of gas required to keep aconstant pressure in the tank should be the flow rate of the leak. Basedon this flow rate and the pressure in the tank, the size of the hole inthe tank may be calculated and compared to a calibration standard.

Once a hole size is determined by the constant flow method, the tank maybe allowed to leak down over a predetermine period. Based on thepressure drop in the tank versus time, the volume of the tank may becalculated. If the tank does not have any leaks, the volume may becalculated based on the Fast Fill Flow time and Fast Fill Flow rate.

Constant Flow Test

In another embodiment of the invention, the test module may perform aconstant flow test. The constant flow test may operate by applying aconstant flow of air to the fuel tank which may result in a increasingpressure. By measuring the rate at which a pressure corresponding to thepressure in the fuel tank increases, a determination may be made as tothe integrity of the fuel tank (or fuel system). The pressure inside anun-compromised fuel tank would increase at a greater rate than thatinside a compromised fuel tank. In some embodiments, the degree to whichthe fuel tank is compromised may be determined by the rate at which thepressure inside the fuel tank increases.

Leak Down

According to embodiment, the test module may test the integrity of afuel tank using a leak down test. In performing the leak down test, thetank tester may pressurize the fuel tank to a predetermined pressure.Once the predetermined pressure is reached, a time interval elapses, andthe pressure in the fuel tank is measured. Successive time intervals andpressure measurements may occur. If the pressure in the fuel tankremains approximately at the predetermined pressure, the fuel tank (orfuel system) may not be compromised (e.g., no leaks, or leaks within anaccepted tolerance). If the pressure in the fuel tank decreases, thefuel tank (or fuel system) is most likely comprised (e.g., has a leak).The tank tester may then perform calculations to determine the size ofthe leak and whether the leak is acceptable (e.g., pass/fail).

Vacuum Testing

According to an embodiment of the invention, the test module maydetermine the integrity of a fuel tank (or fuel system) using vacuumtesting. In one embodiment, vacuum testing may comprise reducingpressure in a fuel tank to a predetermined pressure below ambientpressure. Such a predetermined pressure may be achieved by applying avacuum to the fuel tank. Once the predetermined pressure is reached, apressure corresponding to the pressure in the fuel tank is measured. Ifthe pressure in the fuel tank remains approximately at the predeterminedpressure, the fuel tank (or fuel system) may not be compromised (e.g.,no leaks, or leaks within an accepted tolerance). If the pressure in thefuel tank increases, the fuel tank (or fuel system) may be comprised(e.g., has a leak). The tank tester may then perform calculations todetermine the size of the leak and whether the leak is acceptable (e.g.,pass/fail).

In another embodiment of the invention, vacuum testing may includeapplying a continuous vacuum to a fuel tank which results in adecreasing pressure inside the fuel tank. By measuring the rate at whicha pressure corresponding to the pressure in the fuel tank decreases, adetermination may be made as to the integrity of the fuel tank (or fuelsystem). The pressure inside an uncompromised fuel tank would decreaseat a greater rate than that inside a compromised fuel tank. In someembodiments, the degree to which the fuel tank is compromised may bedetermined by the rate at which the pressure inside the fuel tankdecreases.

Mechanical Pressure

According to one aspect of the invention, the test module of the tanktester may determine the integrity of the fuel tank (or fuel system) byapplying a constant, predetermined pressure to the fuel tank via amechanical device, such as a piston and cylinder. A force may be appliedto the piston commensurate with the desired predetermined pressure to beapplied to the fuel tank. Once a predetermined pressure has been reachedin the tank, the force applied to the piston and the force correspondingto the pressure in the fuel tank should be equal and opposite. If thefuel system is uncompromised (e.g., no leaks), the piston should remainstationary (or nearly so). If the fuel system is compromised (e.g.,leaks), the piston should move. The degree to which the piston moves isrelated to the degree to which the fuel system leaks. The movement ofthe piston in the cylinder may be measured via various well knownmechanisms.

Manual Mode

In one embodiment of the invention, the tank tester may include amanual-test module. The manual-test module may perform a manual testsequence. In performing the manual test sequence a user may first selectthe manual test mode, connect the tank tester to a fuel tank, andinitiate a manual test. The tank tester may then pressurize the fueltank to a predetermined pressure level such as, for example, 14″ H₂O.The tank tester may maintain that pressure for a predetermined timeperiod. During pressurization, a user may take readings from the varioussensors and transducers of the tank tester for use in determining thevarious qualities of a fuel tank being tested. At the end of thepredetermined time period, the tester may vent any remaining tankpressure.

Multiple Standards

The test module may utilize different predefined standards for fuel tanktests. In one embodiment, a standard may be defined as a leak thatexceeds an equivalent size gap. For example, the test module may base apass/fail determination on a standard of a 0.020″ gap. Where a fuelevaporative system leak is less than or equal to a 0.020″ diameter gapthe test module may return a pass determination. Accordingly, the testmodule may fail the fuel evaporative system where the leak exceeds a0.020″ diameter gap.

Under a different standard such as, for instance, a 0.040″ diameter gapstandard, the test module may pass a vehicle where the fuel evaporativesystem leak is less than or equal to a 0.040″ diameter gap, and fail thefuel evaporative system where the leak exceeds a 0.040″ diameter gap.The false pass error rate may be less than ±5% and the false fail errorrate may be less than ±1%. Other pass/fail standards and error rates maybe used. All data pertinent to test standards may be stored in a file.This file may contain any and all data and/or algorithms required tomake the Pass/Fail decision in the tank tester.

Calculations and Compensation

According to one aspect of the invention, the tank tester may furthercomprise a data analysis module. The data analysis module may, amongother things, measure vapor space, temperature, and Reid Vapor Pressure(RVP) within a fuel tank being tested, and may compensate for thesefactors when making test calculations.

Temperature measurements may be taken by one or more temperature sensorsincluded in the tank tester. The temperature sensors may be placed invarious locations within the testing component, and may be connected toa sensor or other element of the computer component of the tank tester.Additionally, various hardware and/or software components associatedwith the tank tester may be used to determine liquid fuel temperaturebased on measured vapor temperature. These temperature readings may beused in the calculations made during the various tests performed by thetank tester.

The tank tester may also include a barometric pressure sensor that mayenable measurement of the barometric pressure of the testing environmentin which the tank tester is being used. The testing component may alsoinclude an ambient temperature sensor that may enable measurement of theambient temperature of the testing environment. These measurements mayalso be used in the calculations performed by the tank tester.

Reid Vapor Pressure (RVP) measurements may also be taken for the fuel ina fuel tank. RVP corresponds to the pressure induced in a closed volume(fuel tank) as a result of the liquid (fuel) in the closed volumeevaporating. To improve the accuracy of the tank tester, the dataanalysis module may compensate for the RVP. In order to compute RVP, thedata analysis module may obtain the following measurements orquantities: the volume of the fuel tank, the volume of the liquid in thetank, a measure of the liquid's tendency to evaporate, and the ambienttemperature. With these variables, the amount of pressure induced by theevaporative effects of the fuel may determined.

In some embodiments of the invention, the RVP may be measured directlyby, for instance, releasing the pressure in the fuel tank, resealing thefuel tank, allowing the closed system to reach a steady state condition,and measuring the RVP at steady state. Once the RVP is determined, thedata analysis module may compensate for RVP in its pressure measurementsas would be apparent.

In some embodiments, certain other measurements such as, for example thevolume of the fuel tank, the volume of fuel in a fuel tank, the volumeof vapor in the fuel tank, or other measurements, may be used by thetank tester in making calculations. In some embodiments, the volume ofthe fuel tank may be provided by the manufacturer of the fuel tank orintegrator of the fuel system (e.g., an automobile manufacturer). Inother embodiments, the volume of the fuel tank may be measured. In someembodiments, the volume of fuel may be measured. In other embodiments,the fuel tank may be drained and a known volume of fuel may be dispensedinto the fuel tank. In some embodiments, the volume of the fuel tank andthe volume of the liquid (fuel) may be used to determine the volume ofvapor within the fuel tank. In other embodiments, the volume of thevapor may be measured directly without obtaining the volume of the fueltank and/or the volume of the fuel.

Safety Measures

According to an embodiment of the invention, the tank tester may beconfigured to determine an overpressure condition for either an incomingsupply pressure or a regulated test pressure. If at anytime during aprocedure (for example, a fuel evaporative test or manual mode test) thetester inlet pressure from the air pressure regulator exceeds 35 psi (orother predetermined value), the tank tester may cease any test orprocedure in progress. Tank tester software may prevent the tank testerfrom performing a pressurization of the fuel tank until any overpressurecondition has been corrected.

Additionally, if at anytime during a procedure, the fuel tank pressureexceeds 28″ H₂O gauge (or other predetermined emergency pressure level),as measured by the tank tester, the tank tester may open one or morevalves and vent any remaining pressure in the fuel tank. The tank testermay also prevent pressurization of the fuel tank for any procedure untilthe problem has been corrected. In some embodiments, a pressure switchmay enable the release of pressure from the testing component upon thedetection of the predetermined emergency pressure level. The pressureswitch may act as a back-up in the event that a pressure transducer (orother element of the testing component) fails. According to oneembodiment, the pressure switch may be wired in series with one or morevalves within the testing component and may manipulate said valves toprevent over-pressurization as a fail-safe measure.

At anytime during any test sequence, the test may be aborted by theactivation of an abort button operatively connected to the computercomponent of the tank tester. The abort button may cause the tester toimmediately open a system relief valve, write the “Tech. Abort” code tothe Error field of the Test Record (or otherwise record the abortedtest), and subsequently return to a main menu (discussed in detailbelow).

Software Updates

The tank tester may include a software update module. The softwareupdate module may enable the software associated with the tank tester(including the operating application and various software modules) to beupdated in a number of ways. Software associated with the tank testermay be updated by a modem. For example, a built-in modem may dial a1-800 number, allow a query of the tank tester for the software version,and update software modules and databases as required. In anotherembodiment, the tank tester may be connected to a phone line and a hostmay call the tank tester to commence an update process.

In yet another embodiment, software may be updated using a compact flashcard or other memory storage device within the tank tester, which may beremoved from the tank tester, sent to a service provider forreprogramming, and reintroduced into the tank tester with updatedsoftware. Alternatively, memory storage devices containing updatedsoftware may be sent to tank tester users as replacements for olderdevices.

In another embodiment, software may be updated by connecting the tanktester to a personal computer (or other computer). A user may thenconnect to the Internet or other designated network and link to aprovider web page to download software updates. These updates may thenbe communicated to and stored within the tank tester. Alternatively, thetank tester may contain sufficient computer hardware and/or software toconnect to the Internet or other network without the aid of anadditional computer.

Menus

In one embodiment, the tank tester may include a main menu. Any one ormore of the following menu options may be displayed in the main menu (orother menus) and may be facilitated by the tank tester's software and/orhardware: (1) Fuel Evaporative Test, (2) Diagnostic Manual Mode testing,(3) Calibration, (4) Self-test, (4) Status Mode, (5) Software update,(6) Service mode, (7) QA State Menu, or other options.

In one embodiment a Status Mode may display the following information:testing station's license number (or other testing stationidentification); next test record number; tester number; date/time;loaded software version number; update software version number; andtester lock out reason.

In one embodiment, a QA State Menu may provide access to certain datastored on the tank tester. The QA State Menu may be accessed via thetank tester's display device and user input device, a separate computer(such as a laptop), or other device. The QA State Menu may include amenu comprising one or more of the following options: update config.tables, load software update, download test records, downloadcalibration records, lock-out tester, or other options. The QA StateMenu may be password protected via a password protection module of thetank tester. The password protection module may also be used to providepassword protection to any menu or feature of the invention describedherein.

System Communications

According to an embodiment, the tank tester may include a communicationsmodule. The communications module may enable standard RS232communications protocols that may be used for communication between anEIS and the tank tester. In addition, a laptop computer (or othersuitable device) using RS232 communications may be used for software andtable updates for the tank tester. Communications protocols as usedherein may enable users to perform one or more various functionsincluding, for example: updating operating software as deemed necessary;updating tables for pass/fail standards; downloading test data fromrecords stored in the tank tester; downloading tank tester calibrationrecords stored in the tank tester; outputting pass/fail results to theEIS; or communicating with other computers or a network of computers.Furthermore, the communications module may perform updates and othercommunications using a modem incorporated into the tank tester.Protocols other than RS232 may be used.

According to an embodiment of the invention, the tank tester may includea serial mode module for serial mode operation. Serial mode operationmay be two-fold. A first serial mode operation may be for checkout andtesting of production line tank testers and repair of returned tanktesters. A second serial mode operation may be for integratingcommunication to EIS equipment. The configuration of the serial portmay, for instance, have a baud rate fixed at 9600 baud. Other signalingrates may be used.

According to an embodiment, with the tank tester connected to andcommunicating with an EIS, the tank tester may be powered by a 12 VDCsource limited to 0.5 amps supplied by the RS 232 communications port.Other configurations may be implemented. Alternatively, the tank testermay be integrated with an EIS.

According to an embodiment, a development/service mode may also beprovided. The development/service mode may run an evaporative test andshow current pressure, temperature and flow readings during the test andshow results after the test is finished. The development/service modemay also run a manual service and test mode while displaying sensorreadings solenoid or valve status. Furthermore, the development mode mayallow the update of software, databases and tables in conjunction withor apart from other features described herein.

Interlocking Tank Adaptor Safety Mechanism

In one embodiment, the tank adaptor of the tank tester (which interfaceswith and seals the tank tester to the fuel system) may provide a closedsystem between the fuel system and the tank tester. In some embodimentsof the invention, the tank adaptor may allow the tank tester topressurize the fuel system, among other things.

One drawback associated with pressurizing a fuel system may arise when afuel tank is full, or nearly full, of fuel. If the pressure is notproperly released, some fuel may spill or splash out of the tank.According to one aspect of the invention, the tank tester may include aninterlock that prevents fuel from spilling, splashing, or otherwisebeing released from the fuel system when it is depressurized. This maybe accomplished either at (or proximate to) the tank adaptor alone, orin combination with various functionality incorporated into the tanktester.

In some embodiments, the tank adaptor may be unable to be physicallyremoved from the fuel neck until pressure inside the fuel tank returnsto ambient pressure. For example, the tank adaptor may incorporate orotherwise operate with an interlock that prevents the tank adaptor frombeing removed from the fuel neck until pressure inside the tank returnsto ambient pressure.

In some embodiments, the tank adaptor may include a valve (e.g., bleedvalve, etc.) that releases the pressure in the fuel system. In someembodiments, the valve may include an automated valve that controls thereturn of ambient pressure to the fuel tank.

Hydrocarbon Detector

In one embodiment, the tank tester may contain various mechanicalcomponents, hardware components, and/or software components (or modules,such as a hydrocarbon detection module) that may enable the tank testerto detect fuel vapor that escapes from the fuel system. To facilitatefuel vapor detection, a small amount of pressure above ambient pressuremay be applied to the fuel system. This pressure may force any fuelvapor out of a compromised fuel system. Such fuel vapor may be detectedby a detector incorporated into the tank tester such as, for example, agas analyzer or other detector capable of detecting hydrocarbons. Inaddition to detecting whether fuel vapor may be leaking from the fuelsystem, the detector may also be used to determine the approximatelocation of the leak by, for example, using a probe from the detector toidentify areas with increased levels of hydrocarbons. Devices suitablefor hydrocarbon detection are known to those skilled in the art.

Integrated Fuel Cap and Fuel Tank Testing

Currently, tank integrity and fuel cap tests may be performedseparately. According to one aspect of the invention, the tank testermay be modified to contain sufficient devices, as well as computerhardware and/or software to enable simultaneous measurement of fuel capleakage and fuel tank integrity.

These and other objects, features, and advantages of the invention willbe apparent through the detailed description of the preferredembodiments and the drawings attached hereto. It is also to beunderstood that both the foregoing general description and the followingdetailed description are exemplary and not restrictive of the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a tank tester system, according to anembodiment of the invention.

FIG. 2 is an exemplary illustration of various components which may beutilized by a tank tester system, according to an embodiment of theinvention.

FIG. 3 is an exemplary illustration of various components which may beutilized by a tank tester system, according to an embodiment of theinvention.

FIG. 4 is an exemplary illustration of various sensors and plumbingcomponents for use with a tank tester system, according to an embodimentof the invention.

FIG. 5 is an exemplary illustration of various sensors and plumbingcomponents for use with a tank tester system, according to an embodimentof the invention.

FIG. 6 is an exemplary flow chart of a calibration process, according toan embodiment of the invention.

FIG. 7 is an exemplary flow chart of a calibration process, according toan embodiment of the invention.

FIG. 8 is an exemplary flow chart of a calibration process, according toan embodiment of the invention.

FIG. 9 is an exemplary flow chart of a self-test process, according toan embodiment of the invention.

FIG. 10 is an exemplary flow chart of a fuel tank test process,according to an embodiment of the invention.

FIG. 11 is a schematic diagram of a tank tester system, according to anembodiment of the invention.

FIG. 12 is an exemplary flow chart of a manual mode test process,according to an embodiment of the invention.

FIG. 13 is an exemplary flow chart of a password protection process,according to an embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

According to an embodiment illustrated in FIG. 1, a system 100 isprovided for a tank tester 101. Tank tester 101 may be used to test theintegrity of a fuel system 150, as described in greater detail below.Fuel system 150 may include a fuel tank 140, a fuel tank neck 143, fuel145, and/or other elements. Fuel system 150 may by a fuel system for acar, motorcycle, light-duty truck, heavy-duty truck, or other motorvehicle. Tank tester 101 may include a computer-implemented component103 (“computer component 103”), a testing component 117, a housing 130,a calibration tank 135, and/or other elements.

Computer Component

In one embodiment, computer component 103 may include various computerhardware and software elements such as, for example, a processor 105.Processor 105 may be or include, for instance, any of the Intel ×86PC/AT microprocessors or compatible processors such as those availablefrom Cyrix or AMD.

Computer component 103 may include an operating application 107.Operating application 107 may include one or more software modules 109a-109 n enabling the operation of, and user interaction with, tanktester 101. Operating application 107 may be based on any one of manycomputer programming languages such as, for example, C, C++, or otherprogramming language.

In particular, operating application 107 may include a data analysismodule, a test module, a calibration module, a self-test module, amanual test module, a communications module, a serial mode module, asoftware update module, a password protection module, a hydrocarbondetection module, and/or other modules. The features enabled mayinclude, among other things, fuel tank temperature measurement, fueltank pressure measurements, tank tester calibration procedures, fueltank integrity tests, vapor space compensation, temperaturecompensation, Reid Vapor Pressure (RVP) compensation, hydrocarbondetection, interface with an Emissions Inspections System (EIS), andother features. One or more of the modules comprising operatingapplication 107 may be combined. For some purposes, not all modules maybe necessary.

In one embodiment, operating application 107 may also include, or haveaccess to, data look-up tables, and may use table calls for fuel tankvapor space calculations, pass/fail decisions, and/or other calculationsand decisions. These tables may compensate for temperature and RVP whenmaking the vapor space calculations, pass/fail determinations, or othercalculations or decisions. In addition, operating application 107 maywrite test results and calibration test results to a record (“testrecord”).

Computer component 103 may include one or more memory devices 108.Memory device 108 may include, for instance, flash erasable programmableread only memory (FEPROM), hard disk, or other suitable memory for datastorage. Memory device 108 may enable the storage of test records orother results or error files. Memory device 108 may also enable thestorage of any data necessary to perform the functions of tank tester101 described herein.

According to an embodiment of the invention, one or more users mayaccess tank tester 101 and operating application 107 through aninterface. The interface may comprise a graphical user interface (GUI)110 presented to a user on a display device 111. The user may interactwith operating application 107 and GUI 110 via a user input device 113.Display device 111 may be or include, for instance, a display screensuch as a 20″ by 4″ LCD screen. In some embodiments, display device 111may include other types of known display screens.

In one embodiment, user input device 113 may be or include, forinstance, a 4 by 4 digital keypad with various keys. In anotherembodiment, user input device 113 may include a combination of fourbuttons to accommodate one or more of the following functions forscrolling through and selecting items from menus displayed via graphicaluser interface 110: (1) scroll up; (2) scroll down; (3) select (orstart); and (4) abort. Alternately, a rocker type switch may besubstituted to accommodate the scroll up and down function therebyreducing the number of buttons to three. Other configurations arepossible. In some embodiments, user input device 113 may include othertypes of known input devices or keyboards.

In one embodiment, display device 111 may enable interaction with GUI110 via various menus, with which a user may interact, using user inputdevice 113. Both display device 111 and user input device 113 may beoperatively connected to processor 105.

It should be understood that various software modules 109 a-109 nutilized to accomplish the functionalities described herein may bemaintained on one or more of processor 105, control application 107,memory device 108, or other components of the system. In otherembodiments, as would be appreciated, the functionalities describedherein may be implemented in various combinations of hardware and/orfirmware, in addition to, or instead of, software.

In one embodiment, tank tester 101 may also include an outlet hose 121.Outlet hose 121 may include a section of pneumatic conduit that mayenable pneumatic connection between tank tester 101 and fuel system 150.One end of outlet hose 121 may terminate in a tank adaptor 123. Tankadaptor 123 may be one of a set of fuel tank filler neck adaptors thatmay interface with fuel neck 143, regardless of the make or model of thevehicle of which fuel system 150 is a part.

In an embodiment of the invention illustrated in FIG. 2, an exemplaryconfiguration of computer component 103 may be provided in a system 200.System 200 may include a processor board 201. Processor board 201 mayinclude a processor 203. Processor board 201 may also include, forinstance, one or more analog inputs 205 a-205 n with A/D converters forinterface with various sensors, one or more digital outputs 207 a-207 nto interface with one or more solenoids or other elements. Processorboard 201 may also include one or more serial ports 213 a-213 n whichmay interface with additional equipment such as, for example, EmissionsInspection Systems (EIS) equipment, a modem 216, a real time clock 215,or other elements. Processor board 201 may also include one or morememory devices 217. One or more memory devices 217 may include FEPROM, ahard disk, or other suitable memory for storing data.

System 200 may also include a signal conditioning board 219 operativelyconnected to processor board 201. Signal conditioning board 219 may,among other things, condition electrical signals into and out from anysensors. Such signal conditioning may be accomplished as would beapparent to one skilled in the art. Signal conditioning board 219 mayinclude a DC/DC power supply 223. Power supply 223 may include a 12 volt0.5 amp power supply, although other voltages and amperages may be used.Signal conditioning board 219 may also include a pressure switch control225 which may release pressure from testing component 117 (FIG. 1) whena predetermined pressure is reached within testing component 117. Signalconditioning board 219 may also include one or more solenoid drivers 227a-227 n for operating one or more solenoids throughout tank tester 101.One or more solenoids may be useful for the operation of variouselements of testing component 117 such as, for example, switches,valves, or other elements.

System 200 may include tamper switch 229 operatively connected toprocessor board 201 and/or signal conditioning board 219.

System 200 may include one or more sensors 231 a-231 n operativelyconnected to processor board 201 and/or signal conditioning board 219.One or more sensors 231 a-231 n may include pressure transducers,temperature sensors, or other sensors for the operation of tank tester101.

System 200 may also include external memory 233 operatively connected toprocessor board 201. External memory 233 may include flash memory, ahard disk, or other suitable memory for storing run time programs,vehicle databases, testing lookup tables, recent test results, or otherdata.

Furthermore, computer component 103 may include a display device 235 anda user input device 237 operatively connected to processor board 201.Display device 235 and user input device 237 may be the same as, orsimilar to, display device 111 and user input device 113 described abovewith reference to FIG. 1.

In an embodiment of the invention illustrated in FIG. 3, an alternativeconfiguration of computer component 103 may be provided in a system 300.System 300 may include a processor board 301. Processor board 301 mayinclude a processor 303. Processor board 301 may also include, forinstance, 50 pin compact flash memory 305, 512 kb (or other memory size)flash ROM 307, 512 kb (or other memory size) SRAM 309, a battery 311, areal time clock 313, one or more serial ports 315 a-315 n, a DB9 (orother format) connector 317, a plug in modem card 319 which may includean RJ11 or similar connector, a power input 321 and other elements.

System 300 may also include a signal conditioning board 323 operativelyconnected to processor board 301. System 300 may include one or moresolenoid drivers 325 a-325 n operatively connected to processor boards301 and/or signal conditioning board 323 which may enable the operationof one or more solenoids throughout tank tester 101. System 300 mayinclude a pressure switch 327 operatively connected to processor board301 and/or signal conditioning board 323, which may enable the releaseof pressure from testing component 117 (FIG. 1) upon the existence of apredetermined pressure within testing component 117.

System 300 may also include one or more sensors 329 a-329 n operativelyconnected to processor board 301 and/or signal conditioning board 323.One or more sensors may include, for instance, a inlet pressure sensor329 a, a flow pressure sensor 329 b, a manifold pressure sensor 329 c, aabsolute pressure sensor 329 d, a temperature sensor 329 e, a solenoidpower sensor 329, or other sensors 329 n.

Furthermore, system 300 may include a display device 331 and a userinput device 333 operatively connected to processor board 301. Displaydevice 331 and user input device 333 may be the same as, or similar to,display device 111 and user input device 113 described above withreference to FIG. 1.

Those having skill in the art will appreciate that the aforementionedsystems may work with various configurations. Accordingly, more or lessof the aforementioned system components may be used and/or combined invarious embodiments.

According to one embodiment, the power consumption by tank tester 101may be slightly less than 12 Volts, 0.5 Amps (6 Watts). Otherconfigurations may be implemented. In some embodiments, a 110 VAC wallpack transformer and connector to tank tester 101 may also be provided.

Testing Component

According to an embodiment of the invention, tank tester 101 may includea testing component 117. Testing component 117 may include variouselectronic sensor elements, electronic control elements, and pneumaticpluming elements for performing the operations of tank tester 101described herein.

In an embodiment of the invention illustrated in FIG. 4, an exemplaryconfiguration of testing component 117 may be provided in a system 400.System 400 may include a pressurized gas source 401. Pressurized gassource 401 may contain and/or produce pressurized gas for use in tanktester 101. Pressurized gas may include nitrogen, compressed air, orother gas. If tank tester 101 uses nitrogen as a pressurizing gas, thenitrogen may be 98% pure. Other concentrations may be used. If tanktester 101 uses compressed air as a pressurizing gas, an air filtercapable of removing harmful contaminants and moisture from thecompressed air source may be included. This filter may ensure that nocontaminants enter tank tester 101 that could physically block anyorifice, or chemically contaminate the internal components of tanktester 101. The filter may comprise material known to one of skill inthe art and may be configured to filter down to 5-micron size particles.

Pressurized gas source 401 may reside outside a testing componenthousing 403. In alternative embodiments, pressurized gas source 401 mayreside inside a testing component housing (or other housing) orenclosures associated with tank tester 101.

Pressurized gas source 401 may be pneumatically connected to an inputfilter 404. Input filter 404 may enable filtering of particulates orcontaminates from pressurized gas flowing from pressurized gas source401. Furthermore, a high pressure regulator 402 may be pneumaticallyconnected to pressurized gas source 401 to enable regulation of pressureinto testing component 117. According to an embodiment of the invention,pressure regulator 402 (and other pressure regulators described herein)may enable a controlled flow rate of between two and four liters perminute (LPM). Other flow rates or ranges of flow rates may be achieved.

Pressurized gas source 401 may be pneumatically connected to an inletpressure transducer 405. Pneumatic connection may be accomplished bypneumatic conduit which may comprise material known to one skilled inthe art, suitable to perform the various functions and processesdescribed herein. Inlet pressure transducer 405 may include anelectronic sensor enabling the measurement and communication of pressurelevels to computer component 103. In one embodiment, inlet pressuretransducer 405 may sense pressure ranges from 0-50 pounds per squareinch (psi). Other pressure ranges may be used. Inlet pressure transducer405 may monitor the inlet pressure levels of testing component 117 andcommunicate those pressure levels to computer component 103. Computercomponent 103 may then take appropriate action. For example, if inletpressure levels exceed a predetermined level such as, for instance, 35psi, valves or other elements within testing component 117 may beactivated to correct the situation. According to an embodiment of theinvention, tank tester 101 may be configured to measure inlet pressuresof 0-35 psi within ±10% of point, and internal tank tester pressures of0″-28″ H₂O ±5% of range. Other ranges may be used.

Pressurized gas source 401 may also be pneumatically connected to afirst valve 406. First valve 406 may enable partial or completeobstruction of gas flow through testing component 117. First valve 406may have a first end and a second end. In one embodiment, an inputfilter 404 may be pneumatically connected between pressurized gas source401 and first valve 406. In some embodiments, first valve 406 may be,include, or be controlled by, a mechanism such as, for example, asolenoid driver or other mechanism.

The second end of first valve 406 may be pneumatically connected topressure regulator 407. Pressure regulator 407 may enable a specificflow rate of gas through testing component 117. Pressure regulator 407may be pneumatically connected to a second valve 409. Second valve 409may enable partial or complete obstruction of gas flow through testingcomponent 117. Second valve 409 may have a first end and a second end.In one embodiment, the first end of second valve may be pneumaticallyconnected to pressure regulator 407. In some embodiments, second valve409 may be, include, or be controlled by a mechanism such as, forexample, a solenoid driver or other mechanism.

The second end of second valve 409 may be pneumatically connected to anorifice 410. Orifice 410 may include a section of pneumatic conduit ofpredetermined inner diameter through which gas may flow. When open,orifice 410 may include an inner diameter of 0.023 centimeters. Otherdiameters may be used for orifice 410. Orifice 410 may enable thecontrolled flow of gas through testing component 117 and may becontrolled by an electronic switch.

Orifice 410 may be pneumatically connected to air reservoir 411. Airreservoir 411 may include an enclosure in which gas may be stored and/orthrough which gas may flow. In one embodiment, air reservoir 411 mayhold up to 0.34 liters of gas. In other embodiments other volumes of gasmay be held in air reservoir 411.

An outlet hose 413 may be pneumatically connected to air reservoir 411.In alternative embodiments outlet hose 413 may be connected directly toorifice 410, the second end of second valve 409 or other element oftesting component 117. Outlet hose 413 may have first and second ends.The first end of outlet hose 413 may be pneumatically connected to airreservoir or other element of testing component 117. The second end ofoutlet hose 413 may end in tank adaptor 415. Tank adaptor 415 mayinclude a set of fuel filler neck adaptors that provide connectivity tovarious vehicles.

According to an embodiment of the invention, tank adaptor 415, outlethose 413, and any pneumatic conduit or gasket materials may be pliableand impermeable to some or all gasoline constituents including, forinstance, Methyl Tertiary Butyl Ether (MTBE), ethanol, and methanol.Furthermore, tank adaptor 415, outlet hose 413, and other elementswithin testing component 117 may be fitted with quick disconnectcouplers that facilitate easy and rapid connection and disconnectionfrom the vehicle.

A differential transducer 417 may be pneumatically connected between thesecond end of second valve 409 and orifice 410. Differential transducer417 may also be pneumatically connected to air reservoir 411.Differential transducer 417 may include an electronic sensor enablingthe measurement and communication of pressure levels to computercomponent 103. In one embodiment, differential transducer 417 may sensepressure ranges from 0-14.5 psi. Other pressure ranges may be used.Differential transducer 417 may measure the pressure differentialbetween a section of pneumatic conduit prior to orifice 410 and airreservoir 411.

A reservoir pressure transducer 419 may be pneumatically connected toair reservoir 411. Reservoir pressure transducer 419 may include anelectronic sensor enabling the measurement and communication of pressurelevels in air reservoir 411 to computer component 103. In oneembodiment, reservoir pressure transducer 419 may sense pressure rangesfrom 0-40″ H₂O. Other pressure ranges may be used.

A third valve 421 may be pneumatically connected to air reservoir 411.Third valve 421 may enable partial or complete obstruction of gas flowthrough testing component 117. Third valve 421 may have a first end anda second end. In one embodiment, the first end of third valve may bepneumatically connected to air reservoir 411. In some embodiments, thirdvalve 421 may be, include, or be controlled by a mechanism such as, forexample, a solenoid driver or other mechanism.

The second end of third valve 421 may be pneumatically connected to avent outlet 423. Vent outlet 423 may enable the outlet of gas fromtesting component 117. In some embodiments vent outlet 423 may bepneumatically connected to a filter and/or an outlet canister. Forexample, at the conclusion of a test, compressed fuel tank fumes mayvent through vent outlet 423 into a charcoal canister. The remainingfuel tank fumes may be vented back though tank tester 101's valves to analternate outlet. Testing component 117's alternate outlet may be routedout of a test facility (e.g., a building or other environment) or intoanother area/container. According to one embodiment, tank tester 101 maybe fully vented to a separate container such as, for instance, acharcoal canister, that may be purged on a next (or other subsequent)test cycle.

A check valve 425 may be pneumatically connected to air reservoir 411.Check valve 425 may enable the release of gas to preventover-pressurization. Check valve 425 may operate to allow such releaseupon a occurrence of a predetermined pressure level within testingcomponent 117 such as, for instance, 1 psi or other predeterminedpressure level (“cracking pressure”). Check valve 425 may have a firstend and a second end. In one embodiment, the first end of check valve425 may be pneumatically connected to air reservoir 411. In someembodiments, check valve 425 may be, include, or be controlled by amechanism such as, for example, a solenoid driver or other mechanism.The second end of check valve 425 may be pneumatically connected to ventoutlet 423.

A pressure switch 427 may be connected to testing component 117.Pressure switch 427 may include an electronic and/or mechanical switchthat may open one or more valves to release pressure from testingcomponent 117 upon the detection of a predetermined pressure within tanktester 101 or a fuel system being tested. A pressure switch 427 may actas a back-up in the event that a pressure transducer (or other elementof testing component 117) fails. According to one embodiment, pressureswitch 427 may be wired in series with one or more valves within testingcomponent 117, and may manipulate the valves to preventover-pressurization as a fail-safe measure.

A temperature sensor 429 may also be included in testing component 117.Temperature sensor 429 may determine the temperature of gas withintesting unit 117 or a connected fuel system. Temperature sensor 429 maybe placed in various locations within testing component 117 and may beconnected to computer component 103. Testing component 117 may alsoinclude a barometric pressure sensor 431 for detecting the barometricpressure of a testing environment in which tank tester 101 is beingused.

In an embodiment of the invention illustrated in FIG. 5, an alternativeconfiguration of testing component 117 may be provided in a system 500.System 500 may include a pressurized gas source 501. Pressurized gassource 501 may contain and/or produce pressurized gas for use in tanktester 101. Pressurized gas source 501 may be pneumatically connected toinput filter 504. Input filter 504 may enable filtering of particulatesor contaminates from pressurized gas flowing from pressurized gas source501. Furthermore, a high pressure regulator 502 may be pneumaticallyconnected to pressurized gas source 501 to enable regulation of pressureinto testing component 117.

Pressurized gas source 501 may be pneumatically connected to an inletpressure transducer 505. Inlet pressure transducer 505 may include anelectronic sensor for measureing and communicating pressure levels tocomputer component 103. In one embodiment, inlet pressure transducer 505may sense pressure ranges from 0-100 psi. Other pressure ranges may beused.

Pressurized gas source 501 may also be pneumatically connected to afirst valve 507. First valve 507 may enable partial or completeobstruction of gas flow through testing component 117. First valve 507may have a first end and a second end. In one embodiment, the first endof first valve 507 may be pneumatically connected to input filter 504and/or pressurized gas source 501. A temperature sensor 506 may beconnected to a section of pneumatic conduit between input filter 504, orpressurized gas source 501, and first valve 507. Temperature sensor 506may also be placed in other areas of testing component 117. Temperaturesensor 506 may measure and communicate gas temperature to computercomponent 103. In some embodiments, tank tester 101 may include anambient temperature sensor for measuring the temperature of asurrounding testing environment.

The second end of first valve 507 may be pneumatically connected to afirst orifice 509. First orifice 509 may include a section of pneumaticconduit of predetermined inner diameter through which gas may flow. Whenopen, first orifice 509 may include an inner diameter of 0.024centimeters. Other diameters may be used. First orifice 509 may enablecontrolled flow of gas through testing component 117 and may becontrolled by an electronic switch connected to computer component 103.

First orifice 509 may be pneumatically connected to manifold transducer511. Manifold transducer 511 may include an electronic sensor formeasuring and communicating pressure levels to computer component 103.In one embodiment, manifold transducer 511 may sense pressure rangesfrom 0-1.45 psi. Other pressure ranges may be used.

First orifice 509 may be pneumatically connected to a pressure switch513. Pressure switch 513 may include an electronic and/or mechanicalswitch that may enable the release of pressure from testing component117 via one or more valves upon the detection of a predeterminedpressure such as, for instance, 25″ H₂O or other pressure level.

First orifice 509 may be pneumatically connected to outlet filter 515.Outlet filter 515 may include an activated charcoal filter or otherfilter for removing particulates and impurities from gas traveling intoan outlet hose 517. Outlet hose 517 may have first and second ends. Thefirst end of outlet hose 517 may be pneumatically connected to outletfilter 515. In alternative embodiments, the first end of outlet hose 517may not be connected to outlet filter 515, but may rather be connectedto first orifice 509, to the second end of first valve 507, or toanother element of testing component 117. The second end of outlet hose517 may terminate in tank adaptor 519.

Pressurized gas source 501 may also be pneumatically connected to asecond valve 521. Second valve 521 may enable partial or completeobstruction of gas flow through testing component 117. Second valve 521may have a first end and a second end. In one embodiment, the first endof second valve 521 may be pneumatically connected to input filter 504and/or pressurized gas source 501. In some embodiments, second valve 521may be, include, or be controlled by a mechanism such as, for example, asolenoid driver or other mechanism.

The second end of second valve 521 may be pneumatically connected to asecond orifice 523. Second orifice 523 may include a section ofpneumatic conduit of predetermined inner diameter through which gas mayflow. When open, second orifice 523 may include an inner diameter of0.022 centimeters. Other diameters may be used. Second orifice 523 mayenable the controlled flow of gas through testing component 117, and maybe controlled by an electronic switch connected to computer component103.

Second orifice 523 may be pneumatically connected to a pressureregulator 525. Pressure regulator 525 may enable the controlled flow ofgas through testing component 117. Pressure regulator may bepneumatically connected to a section of pneumatic conduit between firstorifice 509 and outlet filter 515, or may be otherwise pneumaticallyconnected to outlet hose 517.

A differential transducer 527 may be pneumatically connected to asection of pneumatic conduit located between the second end of secondvalve 521 and second orifice 523. Differential transducer 527 may alsobe pneumatically connected to a section of pneumatic conduit locatedbetween second orifice 523 and pressure regulator 525. Differentialtransducer 527 may include an electronic sensor for measuring andcommunicating pressure levels to computer component 103. In oneembodiment, differential transducer 527 may sense pressure ranges from0-14.5 pounds per square inch (PSI). Other pressure ranges may be used.Differential transducer 527 may measure the pressure differentialbetween a section of pneumatic conduit on either side of second orifice523.

A vent outlet 529 may be pneumatically connected to a section ofpneumatic conduit located between first valve 507 and outlet hose 517.Vent outlet 529 may enable the outlet of pressure and gas from testingcomponent 117. In some embodiments vent outlet may be pneumaticallyconnected to a filter and/or an outlet tank.

A check valve 531 may be pneumatically connected to testing component117. Check valve 531 may enable the release of pressure from testingcomponent 117 to prevent over-pressurization. Check valve may operate toallow such a release upon reaching a predetermined pressure level withintesting component 117 such as, for instance, 1 psi or otherpredetermined pressure level (“cracking pressure”). In some embodiments,check valve 531 may be, include, or be controlled by a mechanism suchas, for example, a solenoid driver or other mechanism.

A reliefvalve 533 having first and second ends may be pneumaticallyconnected to testing component 117. The first end of relief valve 533may be pneumatically connected to a portion of pneumatic conduit locatedbetween first valve 507 and outlet hose 517. The second end of reliefvalve 533 may be pneumatically connected to vent outlet 529. Reliefvalve 533 may enable partial or complete obstruction of gas flow throughtesting component 117.

Housing and Calibration Tank

According to an embodiment of the invention illustrated in FIG. 1, tanktester 101 may include a housing 130. In one embodiment of theinvention, housing 130 may enclose one or more components (e.g., 103,117) of tank tester 101. In another embodiment of the invention, housing130 may support one or more components of tank tester 101. Thesecomponents may be supported either internally within housing 130,externally to housing 130, or partially internal and partially externalto housing 130. In another embodiment, housing 130 may comprise a customimpact-resistant plastic enclosure with a carrying strap and/or handle.

In one embodiment of the invention, a calibration tank 135 may beincluded in tank tester 101. Calibration tank 135 may form a volume thatmay be pressurized. In some embodiments, housing 130 itself (or aportion thereof) may form calibration tank 135. In these embodiments,housing 130 may be manufactured and assembled so as to form acompartment having a predetermined volume that may be pressurized. Invarious embodiments, the volume of calibration tank 135 may comprise onegallon, two gallons, five gallons, ten gallons or any otherpredetermined volume. In some embodiments this volume may be adjustable.Calibration tank 135 may also be constructed to withstand an internalpressure of at least 20″ H₂O. Other pressure tolerances may be used.Furthermore, calibration tank 135 may be resistant to shock or othernormal conditions present in an automotive repair shop or otherenvironment with no more than 1% (or other percentage) deformation.

In one embodiment, calibration tank 135 may include a bladder (nototherwise illustrated). In some embodiments, the bladder may conformitself within housing 130. As discussed above, the bladder may compriseany predetermined volume that may also be pressurized.

In another embodiment, housing 130 and/or calibration tank 135 mayinclude a blow-molded case (not otherwise illustrated) having apredetermined volume that may be pressurized. As discussed above, thecase may be formed, machined, or molded to have any predeterminedvolume.

Calibration

According to an embodiment of the invention, tank tester 101 may includea calibration module. The calibration module may be utilized tocalibrate various elements of tank tester 101. Calibration may be usedto adjust and confirm the consistency and accuracy of tank tester 101'svapor space calculations, for various test pass/fail determinations, orfor other calculations. Calibration may include, for example,pressurization of tank tester 101's internal components to check forleaks, calculation of a known calibration tank volume, testing of acalibration tank configured to pass, testing of a calibration tankconfigured to fail, or other procedures. Calibration may also includevarious self-tests of the tank tester 101's transducers, temperaturesensors, or other components.

According to one embodiment, the calibration module may utilize aninternal clock (e.g., real time clock 215 of FIG. 2) to determine whencalibration is due. As an example, the calibration module mayautomatically lock out test procedures on tank tester 101 every 72 hourspending a successful completion of one or more calibration procedures.Other time intervals may be used.

FIG. 6 illustrates an exemplary process 600, wherein the calibrationmodule of tank tester 101 may test the internal integrity of testingcomponent 117. This may be referred to herein as “phase one” of tanktester 101's calibration procedure. In an operation 601, an event mayoccur wherein automated calibration of tank tester 101 is initiated.This event may include, the passage of a predetermined amount of time,the completion of a predetermined number of tests, user selection of acalibration mode, or other event. In an operation 603, the displaydevice 111 (FIG. 1) of tank tester 101 may display a prompt such as, forexample: “INSTALL CAL. ADAPTOR. PRESS START.” As used herein, “prompt”may include any message displayed to a user conveying informationregarding tank tester 101. In an operation 605, a user may install acalibration adaptor to plug outlet hose 121 (FIG. 1) of tank tester 101thus enabling internal pressurization. Also, in an operation 605, thecalibration procedure may be commenced by a user, for example, by theuser pressing a start button that is operatively connected to computercomponent 103 (FIG. 1) of tank tester 101. After the calibrationprocedure is commenced in operation 605, an operation 607 may occur, inwhich tank tester 101 may display the following prompt: “CALIBRATIONSEQUENCE IN PROGRESS.” Other prompts conveying a similar message may beused. In an operation 609, tank tester 101 may pressurize its internalplumbing and external hose to 14″ H₂O. Other pressure thresholds may beused. In an operation 611, the pressurized gas source may be turned offand one or more internal pressure sensors (transducers) may monitor theinternal pressure decay.

If, in an operation 613, the system pressure decay exceeds apredetermined decay threshold such as, for example, 1″ H₂O in 60seconds, tank tester 101 may fail phase one of the calibration test. Inan operation 615, tank tester 101 may display a prompt such as, forexample: “PHASE ONE CAL FAILED.” Other pressure decay levels may be usedto determine the failure of phase one calibration. In an operation 617,tank tester 101 may vent any remaining pressure in tank tester 101 tothe atmosphere. In operation 617 the calibration module may also lockout tank tester 101 and prevent it from performing other proceduresuntil the calibration procedure has been successfully completed. In anoperation 619, the calibration module may write “F” in a PressureDecay-Phase One Result field of a Calibration Record or otherwise recordthe failure of phase one of the calibration procedure. In an operation621, tank tester 101 may display the following prompt: “REMOVE CALADAPTOR” and return to the main menu of tank tester 101 (described indetail below). Other prompts conveying similar messages may be used. If,in operation 613, tank tester 101 does not exceed the predeterminedpressure decay threshold, and thus successfully completes phase one ofthe calibration procedure, tank tester 101 may, in an operation 623,indicate passage of phase one by displaying a prompt conveying such amessage. In some embodiments, the calibration module may then proceed tophase two of the calibration procedure.

FIG. 7 illustrates exemplary process 700, in which the calibrationmodule of tank tester 101 may test and/or calibrate tank tester 101'sability to determine the volume of a tank. This may be referred toherein as “phase two” of tank tester 101's calibration procedure and maybe triggered by the successful completion of phase one or other event.

In an operation 701, tank tester 101 may display a prompt such as, forexample: “CONNECT THE CAL TANK TO THE TESTER. TURN CAL. LEAK SWITCH TOOFF.” In an operation 703, a user may connect a calibration tank to tanktester 101. In an operation 705, while compensating for temperature,tank tester 101 may pressurize the calibration tank to a predeterminedpressure level such as, for instance, 14″ H₂O or other pressure level.Having the exact volume of the calibration tank stored in memory, tanktester 101 may then, in an operation 707, calculate the volume of thecalibration tank. In an operation 709, tank tester 101 may then comparethe calculated volume of the calibration tank with the calibration tankvolume stored in memory. If, in an operation 71 1, the calculated volumediffers from the stored volume exceeding a level of ±10% or otherbenchmark, tank tester 101 may fail phase two of calibration, and in anoperation 713, may display a prompt such as, for example: “PHASE TWO CALFAILED. DISCONNECT TESTER FROM CAL TANK.” In an operation 715, tanktester 101 may vent any remaining pressure to the atmosphere and thecalibration module may lock out tank tester 101 to prevent furtherprocedures until tank tester 101 successfully passes the calibrationprocedure. In an operation 717, the calibration module may write “F” inthe Vapor Space Calculation—Phase Two Result field of the CalibrationRecord or otherwise record the failure of phase two calibration. In anoperation 719, tank tester 101 may return to the main menu.

If, in an operation 711, the calculated volume the calibration tank doesnot differ from the stored volume of the calibration tank exceedingexceed a level of ±10% or other benchmark, and thus successfullycompletes phase two of the calibration procedure, tank tester 101 may,in an operation 721, indicate passage of phase two by displaying aprompt conveying such a message. In some embodiments, the calibrationmodule may then proceed to phase three of the calibration procedure.

FIG. 8 illustrates exemplary process 800, in which the calibrationmodule of tank tester 101 may test and/or calibrate tank tester 101'sability to pass and fail tanks according to a particular test. This maybe known as “phase three” of tank tester 101's calibration procedure andmay be triggered by the successful completion of phase two or otherevent. In an operation 801, tank tester 101 may display a prompt suchas, for example: “SELECT PASS. PRESS START.” In an operation 803, a usermay select “pass” from a menu and may commence calibration by, forexample pressing a start button that is operatively connected tocomputer component 103 (FIG. 1). In an operation 805, tank tester 101may undergo a testing procedure such as, for example, a vapor leak testor other testing procedure, using a calibration tank with the goal ofsimulating a passing test. The integrity of the calibration tank may besuch that the calibration tank should pass the test. For example, if thetest were a vapor leak test, the calibration tank may be configured suchthat no leaks (or insubstantial leaks) are present. If, in an operation807, tank tester 101 determines that the calibration tank passes thetest, tank tester 101 may, in an operation 809, proceed to simulate afailed test of the same type. In operation 809, tank tester 101 maydisplay a prompt such as, for example: “SELECT FAIL. PRESS START.” In anoperation 811, the user may select “fail” from a menu and press thestart button or other button to begin the calibration.

In an operation 813, tank tester 101 may again utilize tank tester 101'stesting procedure, and tests the calibration tank. In this instance thecalibration tank may be configured such that it should fail the test.If, in an operation 815, tank tester 101 fails the test tank, thuspassing phase three of the calibration procedure, tank tester 101 maydisplay a prompt such as, for example: “CAL PASSED. DISCONNECT CAL.TANK” in an operation 817.

If, in operation 807, tank tester 101 fails the test or, in an operation815, tank tester 101 passes the test, and thus fails to properlyidentify the pass or fail conditions of the calibration procedure, then,in an operation 819 tank tester 101 may vent any remaining pressure tothe atmosphere. In operation 819, the calibration module may also lockout tank tester 101 and prevent it from performing procedures or testsuntil tank tester 101 successfully passes the calibration procedure. Inan operation 821, the calibration module may write “F” in the VaporSpace Calculation—Phase Two Result field of the Calibration Record orotherwise record the failure of phase three calibration. In an operation823, tank tester 101 may return to the main menu and display a promptsuch as, for example: “PHASE 3 TESTER CAL FAILED.”

In one embodiment, the calibration module may utilize switichablecalibrated leak standards. To accomplish this, the calibration tank maycontain gaps of different sizes for different standards. The use ofthese orifices may be controlled automatically upon selection of aparticular leak standard. For example, if a 0.020″ standard is selected,a 0.016″ (pass) and 0.024″ (fail) gap may be used in conjunction with acalibration tank for the pass/fail calibration of tank tester 101. If a0.040″ standard is selected, a 0.035″ (pass) and 0.045″ (fail) gap maybe used in conjunction with the calibration tank for the pass/failcalibration of tank tester 101. Other leak standards may be used.Furthermore, if an “Off” position is selected, the calibration tank maybe sealed to create a sealed test container.

Upon successful completion of the calibration procedure, the calibrationmodule may write the results to the calibration record with the date andtime, and start a timer for the next calibration due date and time. Thenew record may be recorded to the calibration record. The data recordedin the calibration record regardless of failure or passage may includeStation ID (facility conducting test), Tester ID (person conductingtest), Calibration ID (the specific calibration iteration), Date/Time ofCalibration, Software Version, Pressure Decay for Phase One, Vapor Spacecalculated for Phase Two, Result of Phase 3, Overall Calibration Result,Calibration Error, Date/Time of Next Calibration Due, or other data. Tocalculate the next time due, the software may add the predetermined timeperiod to the current calibration date and time.

FIG. 9 illustrates an exemplary process 900, wherein a self-test moduleof tank tester 101 may perform a self-test. A self-test may occur with apressurized gas source connected to tank tester 101, and may also occurwith applicable outlet vents of tank tester 101 open.

In an operation 901, a self-test may be initiated by, for example, userselection of a self-test, initiation of a substantive tank test,successful completion of other calibration procedures, or other event.In an operation 903, tank tester 101 may display a prompt such as, forexample: “SELF TEST—PLEASE WAIT” while the self-test module checks toverify that the calibration period has not expired. If, in an operation905, a predetermined calibration period has expired, the self-testmodule may, in an operation 907, display a prompt such as, for example:“CALIBRATION REQUIRED” and return to the main menu.

If, in an operation 905, the predetermined calibration period has notexpired, the self-test module may begin a self-test procedure in anoperation 909. In operation 909, self-test module may test whether tanktester 101's inlet pressure is within a predetermined range while aknown pressure is applied to tank tester 101. If, in an operation 911,inlet pressure falls outside the predetermined range, tank tester 101may proceed to an operation 913. In operation 913, tank tester 101 maydetermine the number of times (within the present self-test) that inletpressure has been self-tested. If a predetermined number of inletpressure self-tests has not been exceeded, then tank tester 101 mayproceed to an operation 915, wherein tank tester 101 may display aprompt such as, for example: “INLET PRESSURE ERROR—CHECK INLET SUPPLYLINE.” The self-test module may then return to operation 909 andreinitiate the inlet pressure test. The self test module may thenproceed through operations 911 and 913. If, in operation 913, tanktester 101 fails the inlet pressure self-test a second time (or otherpredetermined number of times), tank tester 101 may, in an operation917, display a prompt such as, for example: “INLET PRESSURE ERROR, CALLSERVICE.” In an operation 919 the self-test module may return to themain menu without setting a lockout and may record the error.

If, in an operation 911, tank tester 101's inlet pressure falls withinthe predetermined range, then the self-test module may, in an operation921, proceed to test whether tank tester 101's pressure sensors(transducers) fall within a predetermined range. To make thisdetermination, sensor readings are taken while a known pressure isapplied to tank tester 101. If, in an operation 923, the sensors falloutside an expected range, then tank tester 101 may, in an operation925, display a prompt such as, for example: “SENSOR ERROR—CALL SERVICE.”Other prompts conveying similar messages may be used. In an operation,927, the self-test module may return to the main menu without setting alockout and may write the error code Pressure Sensor Error to the testrecord in the Error Code field, or otherwise record the error.

If, in an operation 923, tank tester 101's pressure sensors fall withinthe predetermined range, the self-test module may proceed, in anoperation 929, to test whether tank tester 101's temperature sensorsfall within a predetermined range. This determination may be made bytaking temperature readings from the temperature sensors while a knowntemperature is applied to tank tester 101. If, in an operation 931, thetemperature sensors fall outside the predetermined range, then tanktester 101 may, in an operation 933, display a prompt such as, forexample: “TEMPERATURE SENSOR ERROR—CALL SERVICE.” In an operation 935,the self-testing module may return to the Main Menu without setting alockout and may write the error code Temperature Sensor Error to thetest record in the Error Code field or otherwise record the error.

If, in operation 931, temperature sensors fall within the predeterminedrange, the self-test module may, in an operation 937, determine that theself test has been successfully completed and may display a promptconveying such a message.

According to an embodiment, the calibration module may perform asystem-test for tank tester 101's overpressure function. Thissystem-test monitors for tank tester 101's ability to disable tanktester 101 in the event that over pressurize of a calibration tank orfuel tank occurs. Tank tester 101 may be capable of resuming normaloperation after the overpressure condition has been eliminated, and tanktester 101 successfully completes the calibration proceduresuccessfully. Upon failing the system-test, tank tester 101 may preventfurther testing with the device for a predetermined period of time, butmay allow subsequent attempts to successfully complete calibrationprocedures, self tests or system tests. Once calibration has beensuccessfully completed, the calibration module may allow testing tooccur.

If tank tester 101 fails any portion of a calibration test, a technicianmay be prompted to perform subsequent calibration procedures or contacta designated service provider for repairs. According to one embodiment,when service of tank tester 101 is required, tank tester 101 may notallow further tank testing or manual mode pressurization to be performeduntil full function has been restored by an authorized or designatedservice representative.

Although the calibration procedures described above may have beendescribed as occurring in a particular order (“phase one,” “phase two,”etc.), it should be understood that the aforementioned calibrationprocedures, self-test procedures, and system test procedures may beperformed in any sequence. Any sequence of calibration procedures,self-test procedures, and system test procedures may be referred to as“calibration.”

Testing

Fuel Evaporative Test

Once calibration have been performed, any number of tests, measurements,and/or calculations may be performed. According to an embodiment of theinvention, tank tester 101 may include a test module. The test modulemay enable tank tester 101 to conduct various fuel tank tests such as,for example, a fuel evaporative test. A fuel evaporative test may enablecalculation of the size of a leak in a fuel tank of unknown size.

FIG. 10 illustrates an exemplary process 1000, wherein a test module oftank tester 101 may perform a fuel evaporative test. In an operation1001, fuel evaporative test may be selected from the main menu or a fuelevaporative test may otherwise be initiated. In an operation 1003, tanktester 101 may display a prompt such as, for example: “CONNECT TO TANK,SEAL EVAP SYSTEM, PRESS START.” In an operation 1005, a user may thenconnect tank tester 101 to a fuel tank to be tested, seal or otherwiseprepare all necessary systems, and commence the test. The user maycommence the test by, for example, pressing a start button that isoperatively connected to computer component 103 (FIG. 1).

In an operation 1007, tank tester 101 may pressurize the fuel tank.During or after pressurization, tank tester 101 may determine if themaximum allowable fill time has been exceeded. For example, a gross leakmay be indicated if the fuel tank cannot be pressurized to 5″ H₂O in thefirst 60 seconds of fill time. If, in an operation 1009, the fill timehas been exceeded, tank tester 101 may proceed to an operation 1011. Inoperation 1011, the test module may determine how many times operation1007 has been performed. If operation 1007 has not been performed morethan a predetermined number of times, then tank tester 101 may, in anoperation 1013, display a prompt such as, for example: “GROSS LEAKDETECTED. CHECK ALL CONNECTIONS AND PRESS START.” The test module maythen return to operation 1007 and reinitiate pressurization.

The test module may then proceed through operations 1009 and 1011. If,in operation 1011, operation 1007 has been performed more than thepredetermined number of times, the test module may, in an operation1015, display a prompt such as, for example: “TEST FAILED. TESTCOMPLETE.” Other prompts conveying similar messages may be used. In anoperation 1017, the test module may write a “G” (for “gross leak”) tothe “Test Result” field of the Test Record or otherwise record thefailure and may then display a prompt such as, for example: “UNSEAL EVAPSYSTEM. DISCONNECT TESTER.” In an operation 1019, tank tester 101 maymonitor the fuel tank pressure for 30 seconds (or other time period)after which, tank tester 101 may vent any remaining pressure from tanktester 101 and may return to the main menu.

If, in an operation 1009, the fuel tank passes the fill-time portion ofthe test (indicating no gross leak), the test module may, in anoperation 1021, determine whether an otherwise unacceptable leak existsin the fuel tank (e.g., pass or fail) and make vapor space calculations.In making such calculations, the test module may compensate fortemperature, Reid Vapor Pressure (RVP), and vapor space (described indetail below). Temperature, RVP, and vapor space compensation may beused to ensure accuracy of pressure, volume, and leak measurements.

In operation 1021, the test module may write the ambient temperature tothe “Ambient Temp” field of the test record or otherwise record theambient temperature during the test. In operation 1021, the test modulemay also write the calculated vapor space results to the “Vapor Space”field of the test record or otherwise record the vapor space results. Ifthe fuel tank passes the test, then, in operation 1021, the test modulemay write a “P” to the Test Result field of the Test Record or otherwiserecord passage of the test. In an operation 1023, tank tester 101 maydisplay a prompt such as, for example: “TEST PASSED. PRESS START TOCONTINUE.” Similar steps may be taken in the event of fuel tank failure.In an operation 1025 the user may press the start button or otherwiseindicate readiness to disengage tank tester 101 from the tested fuelsystem. In an operation 1027, tank tester 101 may display a prompt suchas, for example: “UNSEAL EVAP SYSTEM. DISCONNECT TESTER.” If tank tester101 senses any pressure in the fuel tank 10 seconds (or otherpredetermined amount of time) after the last prompt, tank tester 101 mayautomatically vent the remaining pressure from the tank and testingcomponent 117 (FIG. 1) to the atmosphere or other area. In an operation1027, tank tester 101 may turn to the main menu.

Flow Method

In one embodiment of the invention, the test module of tank tester 101may perform a fuel evaporative test designed to calculate the size of ahole in a subject tank using a “flow method.” In this embodiment,testing component 117 of tank tester 101 may have a “Fast Fill Flow” and“Slow Fill Flow” filling path. Using the Fast Fill Flow path, thesubject tank may be pressurized to a predetermined pressure level suchas, for example 14″ H₂O at a rate of approximately 8.5 standard litersper minute (SLPM). Once the desired pressure is realized, tank tester101 may switch to the Slow Fill Flow path. The Slow Fill Flow path mayhave an orifice and precision pressure regulator set to a predeterminedpressure level such as, for example, 14″ H₂O. The pressure regulatorattempts to maintain a constant pressure in the subject tank. If thesubject tank has no leak, there will be no flow. If the subject tank hasa leak, the flow rate of gas required to keep a constant pressure in thesubject tank should be the flow rate of the leak. Based on this flowrate, and the pressure in the subject tank, the size of the hole in thesubject tank may be calculated and compared to a calibrated standard.

Once a hole size is determined by the flow method, the tank may beallowed to leak down over a certain period of time. Based on thepressure drop in the tank versus time, the volume of the tank may becalculated. If the tank does not have any leaks, the volume may becalculated based on the Fast Fill Flow time and Fast Fill Flow rate.

Constant Flow Test

In another embodiment of the invention, the test module of tank tester101 may perform a constant flow test. The constant flow test may operateby applying a constant flow of gas to fuel tank 140 which results in aincreasing pressure. By measuring the rate at which a pressurecorresponding to the pressure in fuel tank 140 increases, adetermination is made as to the integrity of fuel tank 140 (or fuelsystem 150). The pressure inside an un-compromised fuel tank wouldincrease at a greater rate than that of a compromised fuel tank. In someembodiments, the degree to which the fuel tank is compromised may bedetermined by the rate at which the pressure inside the fuel tankincreases.

Leak Down

According one embodiment, the test module may determine the integrity ofa fuel tank using a leak down test. In performing a leak down test, tanktester 101 may pressurize fuel tank 140 to a predetermined pressure.Once the predetermined pressure is reached, a time interval may elapseand a pressure corresponding to the pressure in fuel tank 140 ismeasured. Successive time intervals and pressure measurements may occur.If the pressure in fuel tank 140 remains approximately at thepredetermined pressure, fuel tank 140 (or fuel system 150) may not becompromised (e.g., no leaks, or leaks within an accepted tolerance). Ifthe pressure in fuel tank 140 decreases, fuel tank 140 (or fuel system150) may be comprised (e.g., has a leak). Tank tester 101 may thenperform calculations to determine the size of the leak and whether theleak is acceptable (e.g., pass/fail).

Vacuum Testing

In one embodiment, the test module of tank tester 101 may determine theintegrity of a fuel tank (or fuel system) using vacuum testing. In oneembodiment, vacuum testing may operate by reducing pressure in fuel tank140 to a predetermined pressure below ambient pressure. Such apredetermined pressure may be achieved by applying a vacuum to fuelsystem 150. The vacuum may be applied by a suitable device such as, forexample, a vacuum pump, or other device known to one skilled in the art.Once the predetermined pressure is reached, a pressure corresponding tothe pressure in fuel tank 140 is measured. If the pressure in fuel tank140 remains at approximately the predetermined pressure, fuel tank 140(or fuel system 150) may not be compromised (e.g., no leaks, or leakswithin an accepted tolerance). If the pressure in fuel tank 140increases, fuel tank 140 (or fuel system 150) may be comprised (e.g.,has a leak). Tank tester 101 may then perform calculations to determinethe size of the leak and whether the leak is acceptable (e.g.,pass/fail).

In another embodiment, vacuum testing may operate by applying acontinuous vacuum to fuel tank 140 which results in a decreasingpressure inside fuel tank 140. By measuring the rate at which a pressurecorresponding to the pressure in fuel tank 140 decreases, adetermination may be made as to the integrity of fuel tank 140 (or fuelsystem 150). The pressure inside an uncompromised fuel tank woulddecrease at a greater rate than that inside a compromised fuel tank. Insome embodiments, the degree to which the fuel tank is compromised maybe determined by the rate at which the pressure inside the fuel tankdecreases.

Mechanical Pressure

According to one aspect of the invention illustrated in FIG. 11, thetest module of a system 1100 may determine the integrity of the fueltank 140 (or fuel system 150) by applying a constant, predeterminedpressure to fuel tank 140 via a mechanical device, such as a piston 162and cylinder 160. A force may be applied to piston 162 commensurate withthe desired predetermined pressure to be applied to fuel tank 150. Theforce may be applied to piston 162 by an electric or fuel based motor,by a hydraulic device, or by another suitable device known to oneskilled in the art. Once the predetermined pressure is reached in thetank, the force applied to piston 162 and the force corresponding to thepressure in fuel tank 140 should be equal and opposite. If fuel system150 is uncompromised (e.g., no leaks), piston 162 should remainstationary (or nearly so). If fuel system 150 is compromised (e.g.,leaks), piston 162 should move. The degree to which piston 162 moves maybe related to the degree to which fuel system 150 leaks. The movement ofpiston 162 in cylinder 160 may be measured via various well knownmechanisms.

Manual Mode

In one embodiment of the invention, tank tester 101 may include amanual-test module. FIG. 12 illustrates an exemplary process 1200,wherein a manual-test module of tank tester 101 may perform manual testsequence. In an operation 1201, manual test mode of tank tester 101 maybe initiated. Initiation may occur upon selection by a user or by otherevent. In an operation 1203, tank tester 101 may display a prompt suchas, for example: “PRESS START TO BEGIN TEST.” In an operation 1205, auser may commence the test by, for example, pressing a start button thatis operatively connected to computer component 103 (FIG. 1). In anoperation 1207 tank tester 101 may display a prompt such as, forexample: “SEAL EVAP SYSTEM. CONNECT TO TANK. PRESS START.” In anoperation 1209, a user may connect tank tester 101 to a fuel tank,prepare the system, and continue the test by, for example, pressing thestart button. In an operation 1211, tank tester 101 may pressurize thefuel tank to 14″ of H₂O (or other predetermined pressure level) andmaintain that pressure for no more than 10 minutes or otherpredetermined amount of time. While in the Manual Mode operation, tanktester 101 may display the following prompt: “MANUAL MODE. TIMEREMAINING: XX.” The “XX” may represent the time remaining on thepredetermined amount of time and may count down as the timer elapses. Ifthe user re-initiates the test cycle by, for example, pressing the startbutton prior to the expiration of the predetermined time limit, tanktester 101 may restart the timer and continue to pressurize the fuelevaporative system. This process may be repeated until either the timerexpires or the user aborts the test by, for example, pressing an abortbutton that is operatively connected to computer component 103. Duringpressurization, a user may take readings from the various sensors andtransducers of tank tester 101 for use in determining the variousqualities of a fuel tank being tested. At the end of the predeterminedtime period, in an operation 1213, tank tester 101 may vent anyremaining tank pressure and display a prompt such as, for example: “TESTCOMPLETE. UNSEAL EVAP SYSTEM. DISCONNECT TESTER.” In an operation 1215,the manual-test module may return to the main menu.

If at anytime during the manual mode sequence the testing pressureapplied to the fuel tank exceeds 28″ H₂O (or other predeterminedpressure level), tank tester 101 may automatically abort the manualoperation, open the pressure vent, and display a prompt such as, forexample: “SYSTEM OVERPRESSURE. TEST ABORTED. UNSEAL EVAP SYSTEM.DISCONNECT TESTER.” Tank tester 101 may subsequently lock out the fuelevaporative test and manual mode operation until a successfulcalibration has been completed and return to a main menu.

Additional Components

In some embodiments, tank tester 101 may also include one or moredevices (e.g., pliers/clamps) capable of pinching an outlet hose orother pneumatic conduit to completely block vapor flow. These devicesmay be used during various testing or calibration procedures to blockgas flow through tank tester 101. The devices may apply sufficientpressure to substantially completely block any flow while also leavingthe conduit undamaged and serviceable. In addition, the devices may beself-locking and capable of performing approximately 5,000 clampingcycles.

In one embodiment, tank tester 101 may also include tapered hose plugsthat may plug vapor hose openings in the event that the aforementionedpinching devices are incompatible with the vehicle being tested. Thesehose plugs may be configured to fit ⅛ to ½ inch inner diameter hose in⅛-inch increments. Other configurations may be used. In lieu ofspecially designed plugs, a set of plugs manufactured by Thexton, PartNumber 312, or equivalent may be substituted.

In one embodiment, tank tester 101 may also include a calibrationadaptor designed to plug the end of tank tester 101's hose (thatnormally connects to a tank adaptor). This adaptor may be used to plugtank tester 101's hose end during certain calibration procedures asdescribed above.

Multiple Standards

In one embodiment, the test module may enable the use of differentpredefined standards for fuel tank tests. For example, the test modulemay base a pass/fail determination on a standard on a 0.020″ gap. Wherea fuel evaporative system leak is less than or equal to a 0.020″diameter gap, the test module may return a pass determination.Accordingly, the test module may fail the fuel evaporative system wherethe leak exceeds a 0.020″ diameter gap.

Under a different standard such as, for instance, a 0.040″ diameterorifice standard, the test module may pass a vehicle where the fuelevaporative system leak is less than or equal to a 0.040″ diameter gap,and fail the fuel evaporative system where the leak exceeds a 0.040″diameter gap. The false pass error rate may be less than ±5% and thefalse fail error rate may be less than ±1%. Other pass/fail standardsand error rates may be used. All data pertinent to test standards may bestored in a file. This file may include any or all data and/oralgorithms required to make the Pass/Fail decision in tank tester 101.

Calculations and Compensation

According to one aspect of the invention, tank tester 101 may contain adata analysis module. The data analysis module may, among other things,measure vapor space, temperature, and Reid Vapor Pressure (RVP) within afuel tank being tested and may compensate for these factors when makingtest calculations.

Temperature measurements may be taken by one or more temperature sensorsincluded in tank tester 101. The temperature sensors may be placed invarious places within the testing component and may be connected to asensor or other element of computer component 103. Additionally, varioushardware and software components associated with tank tester 101 may beused to determine liquid fuel temperature based on measured vaportemperature. These temperature readings may be used in the calculationsmade during the various tests performed by tank tester 101.

Tank tester 101 may include a barometric pressure sensor for measuringthe barometric pressure of the testing environment in which tank tester101 is being used. Tank tester 101 may also include an ambienttemperature sensor for measuring the ambient temperature of the testingenvironment. These measurements may also be used in the calculationsperformed by tank tester 101.

Referring back to FIG. 1, Reid Vapor Pressure (RVP) measurements may betaken for a volume of fuel 145 in fuel tank 140. RVP corresponds to thepressure induced in a closed volume (fuel tank 140) as a result of theevaporation of liquid (fuel 145) in the closed volume. To improve theaccuracy of tank tester 101, the data analysis module may compensate forRVP. In order to compute RVP, the data analysis module may obtain thefollowing measurements or quantities: the volume of fuel tank 140, thevolume of the liquid (fuel 145) in fuel tank 140, a measure of theliquid's tendency to evaporate, and the ambient temperature of thesurrounding environment. With one or more of these variables, the amountof pressure induced by the evaporative effects of the fuel 145 may bedetermined.

In some embodiments of the invention, RVP may be measured directly by,for instance, releasing the pressure in fuel tank 140, resealing fueltank 140, allowing the closed system to reach a steady state condition,and measuring RVP at steady state. Once RVP is determined, the dataanalysis module may compensate for RVP in pressure measurements as wouldbe apparent.

In some embodiments, certain other measurements such as, for example thevolume of fuel tank 140, the volume of fuel 145 in fuel tank 140, thevolume of vapor in fuel tank 140, or other measurements may be used bytank tester 101 in making calculations. In some embodiments, the volumeof fuel tank 140 may be provided by the manufacturer of fuel tank 140 orintegrator of fuel system 150 (e.g., automobile manufacturer). In otherembodiments of the invention, the volume of fuel tank 140 may bemeasured. In some embodiments of the invention, the volume of fuel 145in a fuel tank 140 may be measured. In other embodiments, fuel tank 140may be drained and a known volume of fuel 145 may be dispensed into fueltank 140. In some embodiments, the volume of fuel tank 140 and thevolume of fuel 145 may be used to determine the volume of vapor withinfuel tank 140. In other embodiments, the volume of the vapor may bemeasured directly without obtaining the volume of fuel tank 140 and/orthe volume of the fuel 145.

Safety Measures

According to an embodiment of the invention, tank tester 101 may beconfigured to determine an overpressure condition for either an incomingsupply pressure or a regulated test pressure. If at anytime during aprocedure (for example, a fuel evaporative test or manual mode test) thetester inlet pressure from the air pressure regulator exceeds 35 psi (orother predetermined value), tank tester 101 may cease any test orprocedure in progress. Tank tester software may prevent tank tester 101from performing a pressurization of the fuel tank until any overpressurecondition has been corrected.

Additionally, if at anytime during a procedure the fuel tank pressureexceeds 28″ H₂O (or other predetermined pressure level) as measured bytank tester 101, tank tester 101 may open one or more valves and ventany remaining pressure in the fuel tank. Tank tester 101 may alsoprevent pressurization of the fuel tank for any procedure until theproblem has been corrected.

At anytime during a test sequence, the test may be aborted by theactivation of an abort button that is operatively connected to computercomponent 103 (FIG. 1). The abort button may cause tank tester 101 toimmediately open a system relief valve, write the “Tech. Abort” code tothe Error field of the Test Record (or otherwise record the abortedtest), and subsequently return tank tester 101 to the main menu.

Software Updates

A tank tester 101 may include a software update module. The softwareupdate module may enable software associated with tank tester 101(including the operating application and various software modules) to beupdated in a number of ways.

Software associated with tank tester 101 may be updated by a modem. Forexample, a built-in modem may dial a 1-800 number, allow a query of tanktester 101 for the software version, and update software modules anddatabases as required. In another embodiment, tank tester 101 may beconnected to a phone line and a host may call tank tester 101 tocommence an update process.

In yet another embodiment, software may be updated using a compact flashcard or other memory storage device within tank tester 101. Such adevice may be removed from tank tester 101, sent to a service providerfor reprogramming, and reintroduced into tank tester 101 with updatedsoftware. Alternatively, memory storage devices containing updatedsoftware may be sent to tank tester users as replacements for olderdevices.

In another embodiment, software may be updated by connecting tank tester101 to a personal computer (or other computer). A user may then connectto the Internet (or other designated network) and link to a provider webpage to download software updates. These updates may then becommunicated to (and/or stored within) tank tester 101. Alternatively,tank tester 101 may contain sufficient computer hardware and/or softwareto connect to the Internet or other network without the aid of anadditional computer.

Menus

In one embodiment, tank tester 101 may include a main menu. In variousembodiments, any one or more of the following menu options may bedisplayed in the main menu or other menus and may be facilitated by tanktester 101's software and/or hardware: (1) Fuel Evaporative Test, (2)Diagnostic Manual Mode testing, (3) Calibration, (4) Self-test, (4)Status Mode, (5) Software update, (6) Service mode, (7) QA State Menu,or other options.

In one embodiment, a Status Mode may display the following information:testing station's license number (or other testing stationidentification); next test record number; tester number; date/time;loaded software version number; update software version number; andtester lock out reason.

The testing station license number of an entity using tank tester 101may include a license number issued by a state automotive authority orother authority. Other station identification may be used. Stationidentification may be entered into tank tester 101 during initialoperation or startup. In one embodiment, station identification mayconsist of eight characters. In one embodiment, the first two charactersof the identification number may be alphas followed by six digits. Otheridentification number formats may be used.

Tank tester 101 may assign each test a consecutive number (test recordnumber). The number may be written in a Test Record Number field of thetest record or otherwise recorded. In one embodiment, this field may benumeric and have a length of six digits. Furthermore, each tank tester101 may have a unique serial number which may be recorded in the testrecord.

Using an internal clock, tank tester 101 may assign a date/time stamp toeach valid test. A valid test may, in certain embodiments, consist of acompleted fuel evaporative test with a pass/fail result recorded to thetest record. The time may also change to coincide with changes fromstandard time in a particular time zone to daylight savings time. Inaddition, tank tester 101 may compensate for leap year. In oneembodiment, the date and time may be formatted as follows:mmddyyyy₁₃hhmm. The hour stamp may use the 24-hour clock format. Thedate/time may be written to the Test Date/Time field of the test recordor otherwise recorded.

The loaded software version number may contain the version number incurrent use by tank tester 101. The loaded software version number maybe written to the Loaded Software Version Number field of the testrecord or otherwise recorded. This field may be populated in the testrecord for every valid test.

The update software version number may contain the version number ofupdate software that is currently loaded but not being used by tanktester 101. The update software version number may be recorded into afield of the test record. This field of the test record may be populatedif tank tester 101 has update software loaded. At a predetermined date,the software of tank tester 101 may be updated, and the old software maybe discarded. After the update software version turns into the loadedsoftware version, the update software version number field may be blank.

If tank tester 101 has been locked out, then one of the followingreasons (or other reasons) may be displayed on the status page: clockfailure, sensor failure, QA/State tester lockout, or calibrationfailure.

In one embodiment, a QA State Menu may provide access to certain datastored on tank tester 101. The QA State Menu may be accessed via tanktester 101's display device and user input device, a separate computer(such as a laptop), or other device. The QA State Menu may require apassword. In one embodiment, the password may consist of a sixcharacter, case sensitive alphanumeric and may change daily. The accesscode algorithm may be supplied by a service provider or systemadministrator. Other configurations may be implimented.

The QA State Menu may consist of a menu including one or more of thefollowing options: update config. tables, load software update, downloadtest records, download calibration records, lock-out tester, or otheroptions.

FIG. 13 illustrates an exemplary process 1300, wherein the QA State Menu(or other password protected area) of tank tester 101 may be accessed.In an operation 1301, the QA State Menu may be selected. In an operation1303, tank tester 101 may display a prompt such as, for example: “ENTERPASSWORD.” In an operation 1305, a user may enter a password. Whileentering the password, tank tester 101's display device may display onlyX's or other indicators on the screen. In an operation 1307, a passwordprotection module may verify the password. If, in an operation 1309, thepassword is incorrect, the software may proceed to an operation 1311. Inan operation 1311, the password protection module may determine if thenumber of times a password has been entered (“password try”) exceeds apredetermined allowable number. If, in an operation 1311, the number ofpassword tries does not exceed the allowable number, tank tester 101may, in an operation 1313 display a prompt such as, for example:“PASSWORD INCORRECT. REENTER PASSWORD.” The password protection modulemay then return to operation 1305 wherein the user may enter a password.The password protection module may proceed through operations 1307,1309, and 1311. If, in an operation 1311, the number of password triesexceed the allowable number, the password protection module may, in anoperation 1315, return to the main menu and record a password error tothe test record or otherwise record the error. In operation 1315 thepassword protection module may also record the date and time of theerror to the test record.

If, in operation 1309, the password is correct, then the passwordprotection module may (in an operation 1317) display the QA State Menuwhich may contain one or more of the following options: update config.tables, load software update, download test records, downloadcalibration records, lock-out tester, or other option. In someembodiments, the QA State Menu, or other menu, may enable update of tanktester 101's internal clock.

The password protection module is described above for use in conjunctionwith the QA State Menu. The password protection module may, however, beused to provide password protection to any menu or feature of theinvention described herein.

If the update config. tables option is selected form the QA State Menu,the software update module may enable the update of the testingparameter in a Config. Table (or other location) as necessary to improveaccuracy or compliance with mandated guidelines. If the load softwareupdate option is selected, a connected computer may communicate withtank tester 101 to load an updated software version into tank tester101's memory for activation at a later date. If the download testrecords option is selected, a user may access test records and downloadsome or all records to a connected computer. The download may be storedin a unique file on the connected computer identified by Tester ID andStation ID. The process may not delete any records from tank tester 101.If the download calibration records option is selected, a user mayaccess a calibration record and download all records to a connectedcomputer. The download may be stored in a unique file on the connectedcomputer identified by Tester ID and Station ID. The process may notdelete any records from tank tester 101. If the lockout tester option isselected, a user may send a lock out code to tank tester 101 thatprevents tank tester 101 from performing tests or other procedures. Inone embodiment, calibration and or self-tests may not be locked out byselection of the tester lockout option.

Test Record

According to an embodiment, tank tester 101 may record test results andrelated data to a test record. The test record may include multiplefields containing various types of test data such as, for example teststart year, test start month, test start day, test start hour, teststart minute, test start second, vehicle year, vehicle make, vehiclemodel, head space, ambient temp, pressure increase/decrease, test result(pass, fail, abort, etc), abort code, date of last calibration, softwareversion number, and/or other data.

According to an embodiment, a test record may be read from tank tester101 by sending a command with four data bytes in the range of 0000 to9999 (or other range). Tank tester 101 may respond with the data for theselected tank test results as follows:

<STX><echoed command><command data (status bytes)XXXXrr . . . rr><chesksum><ETX>

-   -   →where XXXX is the record number (as requested)    -   →rr . . . rr is the test record data (see above) or all zeros if        no such record has been collected        Other processing alternatives may be implemented.        System Communications

According to an embodiment, tank tester 101 may include a communicationsmodule. The communications module may enable standard RS232communications protocols that may be used for communication between anEIS and tank tester 101. In addition, a laptop computer (or othersuitable device) using RS232 communications may be used for software andtable updates for tank tester 101. Communications protocols as usedherein may enable users to perform one or more various functionsincluding, for example: updating operating software as deemed necessary;updating tables for pass/fail standards; downloading test data fromrecords stored in tank tester 101; downloading tester calibrationrecords stored in tank tester 101; outputting pass/fail results to theEIS; communication with other computers or a network; or other function.Furthermore, the communications module may perform updates and othercommunications using a modem incorporated into tank tester 101.Protocols other than RS232 may be used.

According to an embodiment, tank tester 101 may include a serial modemodule for serial mode operation. Serial mode operation may be two-fold.A first serial mode operation may be for checkout and testing ofproduction line tank testers and repair of returned tank testers. Asecond serial mode operation may be for integrating communication to EISequipment. The configuration of the serial port may, for instance, havea baud rate fixed at 9600 baud. Other signaling rates may be used.

According to an embodiment, when connected to and communicating with anEIS, tank tester 101 may be powered by a 12 VDC source limited to 0.5amps supplied by the RS 232 communications port. Other configurationsmay be implemented. Alternatively, tank tester 101 may be integratedwith an EIS.

According to an embodiment, a service mode may also be provided. Thedevelopment/service mode may run an evaporative test and show currentpressure, temperature and flow readings during the test and show resultsafter the test is finished. The service mode may also run a manualservice and test mode while displaying sensor readings solenoid or valvestatus. Furthermore, the development mode may allow the update ofsoftware, databases and tables in conjunction with or apart from otherfeatures described herein.

Interlocking Tank Adaptor Safety Mechanism.

According to embodiment, the tank adaptor of tank tester 101 (e.g., tankadaptor 415 in FIG. 4 or tank adaptor 519 of FIG. 5) may provide aclosed system between fuel system 150 and tank tester 101. In someembodiments of the invention, tank adaptor 121 may enable tank tester101 to pressurize fuel system 150, among other things.

One drawback associated with pressurizing fuel system 150 may arise inthe event that fuel tank 140 is full, or nearly so, of fuel 145. If thepressure is not properly released, some fuel 145 may spill or splash outof the tank. According to one aspect of the invention, tank tester 101may include an interlock that prevents fuel from spilling, splashing orother being released from fuel system 150 when it is depressurized. Thismay be accomplished either at or proximate to tank adaptor 121 alone orin conjunction with various functionality incorporated into tank tester101.

In some embodiments of the invention, tank adaptor 121 may be unable tobe physically removed from fuel neck 143 until pressure inside fuel tank140 returns to ambient pressure. In some embodiments, tank adaptor 121may incorporate or otherwise operate with an interlock that preventstank adaptor 121 from being removed from fuel neck 143 until thepressure returns to ambient pressure (i.e., the pressure of the testingenvironment).

In some embodiments, tank adaptor 121 may include a valve (e.g., bleedvalve, etc.) that releases the pressure in fuel system 150. In someembodiments, tank tester 101 may include the valve (such as the reliefvalves described in FIGS. 4 and 5). Other embodiments may incorporatethe valve elsewhere as would be apparent. In some embodiments, tanktester 101 may include an automated valve that controls the return ofambient pressure to fuel tank 140.

In one embodiment, a kit containing various tank adaptors may beprovided with tank tester 101. These adaptors may be designed to fit amajority of vehicles' fuel tank filler necks. In case none of theadaptors fit, a universal tank adaptor may be provided. These adaptorsmay be made using materials that may be pliable and impermeable to allgasoline constituents. These adaptors may also be made usingnon-conductive material to prevent sparks.

Hydrocarbon Detector

According to one aspect of the invention, tank tester 101 may containvarious mechanical components, hardware components, and/or softwarecomponents (or modules, such as a hydrocarbon detection module) that mayenable tank tester 101 to detect fuel vapor that escapes from fuelsystem 150. To facilitate fuel vapor detection, a small amount ofpressure above ambient pressure may be applied to fuel system 150. Thispressure may tend to force any fuel vapor out of a compromised fuelsystem 150. Such fuel vapor may be detected by a detector incorporatedinto tank tester 101 such as, for example, a gas analyzer or otherdetector capable of detecting hydrocarbons. In addition to detectingwhether fuel vapor may be leaking from fuel system 150, the detector mayalso be used to determine the approximate location of the leak by, forexample, using a probe from the detector to identify areas withincreased levels of hydrocarbons. Devices suitable for hydrocarbondetection are known to those skilled in the art.

Integrated Fuel Cap and Fuel Tank Testing

Currently, tank integrity and fuel cap tests may be performedseparately. According to one aspect of the invention, tank tester 101may be modified to contain sufficient devices, as well as computerhardware and/or software to enable simultaneous measurement of fuel capleakage and fuel tank integrity.

Other embodiments, uses and advantages of the invention will be apparentto those skilled in the art from consideration of the specification andpractice of the invention disclosed herein. The specification should beconsidered exemplary only, and the scope of the invention is accordinglyintended to be limited only by the following claims.

1. A method for testing the integrity of a fuel tank, comprising:pressurizing a fuel tank at a first predetermined pressurization rate toa predetermined pressure level; and calculating the size of a leak inthe fuel tank by: (i) maintaining the predetermined pressure level inthe fuel tank by applying pressure to the fuel tank at a secondpredetermined pressurization rate if a pressure in the fuel tank dropsbelow the predetermined pressure level; and (ii) measuring an amount ofgas introduced to the fuel tank at the second predeterminedpressurization rate, wherein the size of a leak is proportional to theamount of gas introduced to the fuel tank at the second predeterminedpressurization rate.